In recent years, in a mobile communications system such as a mobile phone, downscaling and energy consumption saving of a portable communications terminal have been strongly demanded. In order to realize these, for example, regarding an antenna switch, it is necessary to reduce an ON resistance Ron or the like. At the present day, as a device in practical use for the purpose of such an antenna switch, there are a Junction Pseudo-morphic High Electron Mobility Transistor (JPHEMT) and the like.
The JPHEMT is a semiconductor apparatus that performs current modulation utilizing a pn junction and a hetero junction. The semiconductor apparatus like this is provided with a hetero junction of, for example, a channel layer made of InGaAs and a barrier layer (AlGaAs) made of AlGaAs whose band gap is wider than that of the channel layer (InGaAs). Within the barrier layer (AlGaAs), a low-resistance region containing impurities is provided in a surface layer opposite to the channel layer, and a gate electrode is connected to this low-resistance region. In addition, within the barrier layer (AlGaAs), a carrier supplying region containing impurities, which turn out to be carriers, is provided on the channel layer side with respect to the low-resistance region. Moreover, a source electrode and a drain electrode are in ohmic contact with the barrier layer (AlGaAs) on both sides of the low-resistance region and the gate electrode.
In the semiconductor apparatus of a configuration as above, in a boundary face in the barrier layer side in the channel layer, a two-dimensional electron gas layer is formed in which electrons serving as carriers are confined at a high concentration. In addition, by applying a voltage to the gate electrode 20 thereby to control a concentration of the two-dimensional electron gas layer, a current flowing between the source electrode and the drain electrode via a channel layer part below the low-resistance region is modulated (regarding the above, see Patent Literature 1 below, for example).